During its life cycle, the unicellular parasite Entamoeba histolytica is challenged by the host immune system which releases oxidative and nitrosative species. Epigenetics is a key factor in the adaptation of invasive species, for its ability to provide a fast response to sadden environmental changes. Our laboratory is studying the mechanisms of adaptation of the parasite to the host environment with a specific emphasis on epigenetic regulation.
Our research activities focus on the characterization of the parasite Dnmt2 enzyme (EhDnmt2). This enzyme belongs to a large family of proteins that are conserved in all species from Schizosaccharomyces pombe to humans. Members of the Dnmt2 family display only low or no (cytosine-5)- DNA MTase activity and a robust tRNA MTase activity, with tRNAAsp, as a preferred substrate. One of the most important contributions of our laboratory to the field was the identification of enolase as the first Dnmt2 interacting protein. Enolase interacts with the catalytic site of EhDnmt2, and inhibits its DNA and tRNA methyltransferase activity. We showed that glucose and more recently nitric oxide regulate the amount of Ehmeth-enolase inhibitory complex and consequently the level of tRNAAsp methylation in the parasite. Our ongoing research focus on the involvement of EhDnmt2 mediated tRNA methylation and other tRNA MTases in the virulence and resistance of the parasite to environmental stresses.
Information about methylated DNA binding proteins in protozoa was inexistent. Our past research has established that methylated LINE binding protein (EhMLBP) is unique to Entamoeba parasites and is involved in DNA methylation recognition. Downregulation of EhMLBP using antisense technology or peptide targeting resulted in trophozoites with impaired growth highlighting EhMLBP as an essential constituent of the parasite E. histolytica and a novel target for anti-amebic chemotherapy. We have recently demonstrated that constitutive overexpression of EhMLBP leads to an enhanced transcription of RT LINE and protects trophozoites against heat shock and reduces protein aggregation. EhMLBP appears in cytoplasmic granules of unknown nature in trophozoites exposed to heat shock. Our ongoing research is aimed at characterizing these granules and interfering with the process of their formation.